This invention relates to cellulose-based animal litter products, and in particular to clumping-type animal litters comprising cellulose-based core particles that are covered with specially designed water-permeable coatings.
American families increasingly prefer cats, with their independent natures and reduced need for care, as compared with dogs. Domesticated animals such as cats are provided in homes with litter boxes, where they dispose of their biological waste. The performance of the litter product in the litter box can vary greatly, depending upon the precise nature of the product. Key attributes of a litter product that are of importance to cat owners are odor control and litter care convenience (that is, supply and removal).
Originally litter products were relatively unsophisticated, and of the type known today as xe2x80x9cnon-clumpingxe2x80x9d. More recently, clumping type cat litters have been introduced. Both types are essentially equivalent with respect to the removal of solids. With both types, solid excretions are scooped out of the litter box daily or at least frequently. However, clumping litters provide great advantages with respect to the way in which urine excretion is handled. Non-clumping litters absorb the urine and hold it until ammonia-type malodors develops, at which time the entire content of the litter box is removed and replaced. Clumping litters, however, are designed to gel when wetted by urine, and the urine soaked granules agglomerate into clumps whose mechanical strength facilitates their removal in the same manner as solid waste is removed, leaving the remaining litter fresh and urine-free.
Litter products have been made with natural substrates or artificial substrates. Natural substrates that have been used include minerals, usually types of clay, or organic matter, usually agricultural byproducts or paper derivatives. Artificial litter particles have generally comprised granules combining several materials of an absorbent nature, aggregated together with a binder to form a granule. These prior art aggregated granules are of a single component naturexe2x80x94that is, all their ingredients are mixed together into one more or less homogeneous entity.
Clumping litters made from bentonite were introduced in 1989, providing better and longer lasting odor control than did traditional litters. Bentonite is a swelling mineral of the clay category, with a unique ability to gel and agglomerate when wetted, creating scoopable clumps. However, mineral based clumping litter are heavy and dusty. While their innate absorption, clumping, and odor control attributes are good, further performance improvement by solid and/or liquid additives is limited.
Organic based clumping litters, on the other hand, make use of the improved absorption capabilities of cellulose fibers. Unfortunately, they have minimal innate clumping properties, and require the addition of clumping agents such as starches and/or polymers. These clumping additives produce litters with much less clumping effectiveness than that of the mineral variety. This lesser clumping performance is apparent from their reduced speed of effective agglomeration, their reduced mechanical strength of the clump, and their duration of cohesion forces in the clumped matter. However, organic clumping litters are lighter in weight, are less dusty, and are flushable, which makes their use more convenient.
U.S. Pat. Nos. 4,949,672; 5,129,365; 5,329,880; 5,361,719; 5,469,809; 5,609,123; and 6,089,189 are typical of patents relating to clumping litters.
U.S. Pat. No. 4,949,672 relates to the use of boron-containing compounds (especially, boric acid) as a urease inhibitor in clumping cat litter. The boric acid is used as a superficial liquid additive, rather than being built into the substrate. The patent claims a method of controlling odor formation in animal litters comprising applying a liquid carrier to particles of absorbent litter substrate, said liquid carrier containing an odor-controlling-effective amount of a boron containing material having an equal boron level of at least about 0.06%.
U.S. Pat. No. 5,129,365 discloses a bentonite-based clumping litter. The odor control performance of such a litter is derived from its natural properties or by commingling odor-control particles with it or by spraying it superficially with odor-control liquids. One disclosed embodiment comprises discrete particles of a combination of non-compacted water-swellable sodium bentonite clay and calcium bentonite clay that effectively absorbs animal dross and simultaneously agglomerates into a water-dispersible but physically stable mass, thereby permitting physical separation of the soiled and wetted bentonite clay particles from discrete particles of the unsoiled and unwetted water-swellable bentonite clay. All ingredient particles in this invention are relatively large, and thus xe2x80x9cmixingxe2x80x9d means between the granules themselves and not within a granule. The mixing of calcium bentonite with sodium bentonite weakens the clump but enables it to be flushable.
U.S. Pat. No. 5,329,880 describes a litter in which a mixture of hydrophilic shale may contain up to 10% clumping agent selected from water absorbent polymers, corn starch, gelatin, gluten, and dried plants of the Plantago family. It is further disclosed that, in addition, 5-25% ammonia-absorbing zeolite may be added for odor control. All ingredient particles in this invention are relatively large, and thus xe2x80x9cmixingxe2x80x9d means between the granules themselves and not within a granule.
U.S. Pat. No. 5,361,719 disclosed a hydrating cat litter which solidifies upon contact with liquids to encapsulate pet waste matter. The litter comprises a mixture of a granulated, organic base material (preferably coarse ground agricultural grains, pulse crops, and/or agricultural byproducts, which support in suspension a quantity of semolina), a gluten-containing material, and optionally a fragrance carrier.
U.S. Pat. No. 5,469,809 describes a single-component granule that combines bentonite and other minerals into an artificial substrate (which contains no fibers). The patent teaches a process that comprises forming a mixture of opal clay with one or more of sodium bentonite, calcium lignosulfonate, and binder, and subsequently pelletizing the mixture.
U.S. Pat. No. 5,609,123 uses superabsorbing polymer as an agglomeration agent on a natural clay substrate. The superabsorbent polymer is sprayed externally and not incorporated as part of a coating complex. The patent claims a method that comprising spraying particulate substrate with a surface-bonding, non-aggregating, amount of moisture, allowing the sprayed moisture to be absorbed onto the surface of the substrate, and mixing the substrate with superabsorbent particles and with clumping particles.
U.S. Pat. No. 6,089,189 discloses cellulose-based clumpable animal litter products that comprise a mixture of adhesive-bearing cellulosic granules and a particulate polymeric clumping agent. The patent claims a process that comprises de-dusting cellulosic granules, contacting the de-dusted granules with water-soluble adhesive, drying the adhesive-bearing granules to a free-flowing state, and combining the dried granules with a particulate polymeric clumping agent to form a uniform admixture. None of these granules has a designed structure, and all ingredient particles in this invention are relatively large, so that xe2x80x9cmixingxe2x80x9d means between the granules themselves and not within a granule.
Applicants are unaware of any prior art that teaches animal litter granules comprising a multi-component functional core coated with a multi-component coating having different functional attributes, as described hereinbelow.
The animal litter of the present invention comprises plural discrete particles which are dual component granules. That is, in accordance with this invention, an absorbent granule is made up of an inner core and an external coating complex. Both the core and the coating comprise aggregates of (different) dry fine powdered materials. The granules of this invention are designed to agglomerate into clumps when wetted. The highly absorptive and lightweight litter of this invention substantially reduces litter box malodors, extends usage duration of a given cat litter volume unit, and increases consumer convenience by substantially reducing the weight of the product in conventionally sized packaging.
Preferably, the inner core of the granule is made with natural or artificial fibers, mineral filler, and binder. More preferably, the fibers in the core are cellulose fibers, most preferably, fine wood fibers. Preferably, the coating of the granule is made with an agglomerating agent and with natural or artificial materials that reduce odors and/or prevent the formation of malodors. More preferably, the coating is mineral or organic or a combination thereof. Most preferably, the external coating layer consists essentially of bentonite, zeolite and/or boric acid, and, optionally, fine cellulose fibers.
In a further embodiment of the present invention, a bactericide, a pH buffer, a deodorizer, a perfume, and/or a de-dusting agent may be sprayed onto the coating layer of the litter granule.
This invention also includes a process for producing the dual constituent absorbent granules. More specifically, this invention provides a process for preparing dual-component granules from fine dry powdered materials, including the preparation of discrete dry mixes for the core and for the coating complex and their subsequent sequential multi-stage arrangement in a predetermined spatial relationship.
Materials that may be employed in practicing the present invention are known for their capabilities to contribute to the task of controlling malodors, and some have previously been used in prior art clumping litters. The present invention is distinguished from such prior art, however, by the novel structure of the disclosed dual-component granule, by its unique powder-only recipes, and by the unique multi-stage process for manufacturing it.
Specifically, this invention provides an animal litter granule formed as a coated core. The core includes 15-45 weight-% dry cellulose fine fibers, 40-80 weight-% dry mineral filler, and 0.5-10 weight-% binder. The coating has a mass that is 0.5-2 times the mass of the core and includes 65-99 weight-% clumping agent, up to 30 weight-% dry cellulose fine fibers, and 1-25 weight-% zeolite or 1-3 weight-% of a boron compound (urease inhibitor) or both of these last two ingredients. The coating may alternatively include 65-94 weight-% clumping agent and 5-30 weight-% dry cellulose fine fibers as well as 1-15 weight-% zeolite and/or 1-3 weight-% of a boron compound.
In the granules of this invention, the coating generally has a mass that is comparable to the mass of the core. That is to say, the mass of the coating of each granule is of the same order of magnitude as is the mass of the core.
The dry cellulose fine fibers in the core (and any cellulose fibers in the coating) typically have a length of 1-3 millimeters and have a moisture content of less than 15 weight-%. These cellulose fibers are preferably selected from the group consisting of wood dust, paper fibers, organic fibers, and mixtures thereof. In the cores of the granules of this invention, the dry mineral filler typically has a particle size range within the range 10 to 150 microns, and has a moisture content of less than 12 weight-%. The mineral filler is preferably selected from the group consisting of lime, fly ash, dolomite, calcium carbonate, and mixtures thereof. The binder in the core is typically selected from the group consisting of starch, acrylic polymer, polyvinyl acetate, guar gum, and mixtures thereof. Most preferably, the binder is unmodified starch granules, 70% of which pass through 200 Mesh U.S. Sieve Series.
In the coating, the clumping agent is normally selected from the group consisting of bentonite clay, starch, and superabsorbent polymer. Typically, the bentonite clay is a sodium montmorillonite having a particle size distribution such that 80% of the particles pass through 200 Mesh U.S. Sieve Series and having a moisture content of less than 12 weight-%. The zeolite component of the coating is most preferably a clinoptilolite having a particle size range within the range 10 to 100 microns and having a moisture content of less than 12 weight-%. The boron compound in the coating is most preferably a boric acid having a particle size range within the range 10 to 100 mesh, U.S. Sieve Series, and having a moisture content of less than 10 weight-%.
The process of this invention produces a highly structured granule with two different sets of functional components. Each of the components is differently formulated and the process places each material in a spatially predetermined position where its performance objectives come into play in an optimal manner. Another important advantage of the present invention is the flexibility and freedom that it provides in changing and xe2x80x9cplaying withxe2x80x9d the formulation, both in the core and in the coating, in order to change ratios between ingredients for achieving desirable specific performance levels for each product performance parameter. The resulting 100% uniform granules deliver unprecedented odor control as well as highly effective agglomerating capabilities.